In the technical literature processes are known for preparing homotelomers of CH.sub.2 .dbd.CF.sub.2 by the action of telogen agents. Also known are copolymers of CF.sub.2 .dbd.CH.sub.2 with fluorinated olefins, obtained in the presence of halogenated telogen agents (Jap. 73-96684 and 84-20310). In the known processes, said telogens, which behave as chain transfer agents, are used in amounts not higher than 1% by mol relatively to the total monomer mols. Thus, polymeric products are obtained, which have a molecular weight not lower than 8000.